pnfs: write: Set mds_offset in the generic layer - it is needed by all LDs

In current pnfs tree, all the layouts set mds_offset in their
.write_pagelist member.
mds_offset is only used by generic layer and should be handled by it.

This patch is for upstream. It is needed in this -rc series to fix a
bug in objects layout_commit.

I'll send patches for objects and blocks to be
squashed into current pnfs tree.

TODO: It looks like the read path needs the same patch.

Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/nfs4filelayout.c

@@ -398,7 +398,6 @@ filelayout_write_pagelist(struct nfs_write_data *data, int sync)
 	 * this offset and save the original offset.
 	 */
 	data->args.offset = filelayout_get_dserver_offset(lseg, offset);
-	data->mds_offset = offset;
 
 	/* Perform an asynchronous write */
 	status = nfs_initiate_write(data, ds->ds_clp->cl_rpcclient,

fs/nfs/write.c

@@ -864,6 +864,8 @@ static int nfs_write_rpcsetup(struct nfs_page *req,
 
 	data->args.fh     = NFS_FH(inode);
 	data->args.offset = req_offset(req) + offset;
+	/* pnfs_set_layoutcommit needs this */
+	data->mds_offset = data->args.offset;
 	data->args.pgbase = req->wb_pgbase + offset;
 	data->args.pages  = data->pagevec;
 	data->args.count  = count;